The morphology of integumental brochosomes in Cicadellidae (Hemiptera: Auchenorrhyncha)

Brochosomes, secretory microstructures composed of protein-lipid compounds, are synthesized in the Malpighian tubules of leafhoppers (Cicadellidae). These specialized particles play essential biological roles, notably providing hydrophobic protection against environmental contaminants and self-generated honeydew residues. This investigation systematically examined the integumental brochosomes morphology in 28 Cicadellidae species representing 12 subfamilies, using optical and scanning electron microscopy (SEM), supplemented by morphological data from 17 additional species extracted from published literature. The resultant comprehensive dataset encompassing 45 species revealed significant morphological divergence in the Hylicinae subfamily relative to other taxa. While most Cicadellidae subfamilies possess submicron-scale brochosomes (<1 μm) with characteristic reticulate surface patterning, Hylicinae specimens exhibited exceptional structural diversity. Detailed analysis of 8 Hylicinae species identified 4 distinct brochosomes morphotypes classified by surface architecture: rugose, ruminate, foveate, and reticulate types, with foveate and reticulate predominating. Notably, interspecific variation persisted within morphological categories, manifesting through: (1) dimensional disparities in reticular unit size, (2) quantitative differences in surface depression density, (3) presence/absence of secondary granular protrusions, and (4) continuity patterns of surface ridges. These diagnostic structural features suggest brochosomes morphology may serve as both a phylogenetic marker and an adaptive trait reflecting ecological specialization within leafhopper lineages.